Offset printing is one type of printing technique. In offset printing that uses engraved plates, after once transferring ink to a rolling blanket roll from an inked, engraved plate (reception), the retransfer of the ink to the print target from the blanket roll (printing) is performed. Thereby, it is possible to print the print pattern of the aforementioned engraved plate with good reproducibility on the surface of the print target.
In recent years, as a method of forming an electrode pattern such as of a liquid crystal display (conductive pattern) on a substrate, instead of fine processing such as etching of a metal vapor-deposited film, there as been provided a formation method that prints the conductive pattern on a substrate serving as a print target using a printing technique that uses a conductive paste as the printing ink, for example, intaglio offset printing technology (for example, refer to Japanese Patent No. 2797567 and Japanese Patent No. 3904433).
In the case of forming an electrode pattern (conductive pattern) such as of a liquid crystal display on a substrate, a fine electrode width of around 10 μm has been sought. Furthermore, in the case of forming a plurality of electrode patterns in a superimposed manner on a substrate, overprinting of the electrode patterns is performed by using different plates. In this case, when the print position shifts, the electrode pattern collapses. Therefore, although the precision required varies somewhat with the target, in a fine electrode pattern in which the electrode width is 10 μm, extremely high positional accuracy is required so as to restrict overlap misalignment to several μm.
As an offset printing apparatus for performing offset printing with high printing accuracy on a print target, a planographic printer is used that employs a planar plate similar to the print target as the plate.
Moreover, as one method of minimizing positioning errors between the blanket roll and the plate or print target when performing offset printing in order to improve the print accuracy, the printing apparatus shown in FIG. 4 has been proposed. In this printing apparatus, sliders 5 and 6 are provided under a plate truck (plate table) 2 that supports a plate bed (not illustrated) on which a flat plate 1 is mounted, and a printing truck (print target table) 4 that supports a printing bed (not illustrated) on which a glass substrate 3 that is the printing target (object to be printed) is mounted. These sliders 5 and 6 respectively have the same dimensions, and are firmly fixed to the bottom of the plate truck 2 and the printing truck 4 in the same arrangement. The plate truck 2 and the printing truck 4 are provided so as to travel (reciprocally move) via the sliders 5 and 6, respectively, on the same rails (guide rails) 7. Moreover, a blanket cylinder (blanket roll) 8 is provided so as to straddle the rails 7.
According to this constitution, even if the straightness of the rails 7 decreases directly under the blanket cylinder 8, and thereby the attitudes of the plate truck 2 and the printing truck 4 tilt at that position, both trucks 2 and 4 will have the same tilt. Accordingly, since attitude errors between the plate 1 and the glass substrate 3 are inhibited, and the transfer between the plate 1 and the blanket cylinder 8 (resin transfer) and the retransfer from the blanket cylinder 8 to the glass substrate 3 (pattern transfer) are performed at the same position, it is possible to increase the printing accuracy (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2008-129362).
Also, Japanese Patent No. 4108012 discloses a resin-coated substrate manufacturing apparatus that is shown in FIG. 5 and FIG. 6. In this resin coated substrate manufacturing device, a left-right pair of guide rails 10 extending in the front-back direction are installed on both sides of a fixed frame 9, and a left-right pair of sliders 11 are slidably attached to the guide rails 10. By attaching on the pair of sliders 11 a left-right pair of movable frames 12 that hold left-right rotating shafts of a transfer cylinder 13 to allow free rotation, it is possible to move the transfer cylinder 13 in the front-back direction, relative to the fixed frame 9, together with the left-right movable frames 12 in tandem with movement of each slider 11 along the guide rail 10. The resin coated substrate is manufactured by letterpress reverse printing to a substrate serving as the print target, not illustrated, that is held on the fixed frame 9, via the transfer cylinder 13, from a relief plate not illustrated that is fixed to the fixed frame 9. Also, a pair of horizontal planes 14 and a pair of vertical planes 15 for supporting the guide rails 10 in a vertical direction and horizontal direction are provided on both side portions of the fixed frame 9 by a polishing process so that the respective linearity may become high. The left-right pair of guide rails 10 are respectively attached and fixed in a pressed state to the horizontal plane 14 and the vertical plane 15, which are provided on the left and right of the fixed frame 9, by a plurality of fixing bolts 16 serving as a horizontal plane pressing portion, and wedge-shaped fixing plates 17 and fixing bolts 18 thereof that serve as a vertical plane fixing portion. Thereby, disturbances to the linearity and parallelism of the guide rails 10 are reduced (for example, refer to Japanese Patent No. 4108012).
However, in the method disclosed in Japanese Unexamined Patent Application, First Publication No. 2008-129362, although it is possible to ensure the position reproducibility of the plate 1 and the print target 3 with respect to the blanket cylinder 8, it is not possible to guarantee absolute straightness accuracy. For that reason, when the plate 1 and the print target 3 advance in a slanted direction with respect to a direction that is at a right angle to the axial center of the blanket cylinder 8 in a state of making contact with the blanket cylinder 8, during the transfer from the plate 1 to the blanket cylinder 8, and when performing the retransfer from the blanket cylinder 8 to the print target 3, there is a possibility of a disturbance occurring in the print pattern. Accordingly, even if it is possible to satisfy the print accuracy that is conventionally required, it is difficult to attain extremely high positional accuracy in the case of there being a need to restrict position misalignment of a fine print pattern, such as in electrode pattern formation, to several μm.
Also, in the device that performs letterpress reverse printing disclosed in Japanese Patent No. 4108012, since the transfer cylinder 13 moves, it is difficult to reduce positional variations when bringing the transfer cylinder 13 into contact with substrates serving as the relief plate or print target, not illustrated, that are held on the fixed frame 9.
Furthermore, in the device disclosed in Japanese Patent No. 4108012, it is possible to reduce disturbances to the linearity and parallelism of the guide rails 10. However, the left and right movable frames 12 that are attached to the sliders 11 that slide along the guide rails 10 are coupled via the transfer cylinder 13 that rotates. Accordingly, when even a slight positional misalignment of the left and right movable frames 12 occurs in the front-back direction, it is no longer possible to cause the transfer cylinder 13 to squarely face the substrates serving as the relief plate or print target, not illustrated, that are fixed on the fixed frame 9. For that reason, even if it is possible to satisfy the print accuracy that is conventionally required, it is difficult to attain extremely high positional accuracy in the case of there being a need to restrict position misalignment of a fine print pattern, such as in electrode pattern formation, to several μm.
The present invention was achieved in view of the above circumstances, and has as its object to provide an offset printing apparatus that can attain positional reproducibility of high accuracy when performing transfer from a plate to a blanket roll, and when performing retransfer from a blanket roll to a print target, and can attain extremely high positional accuracy in the case of there being a need to restrict position misalignment of a fine print pattern, such as in electrode pattern formation, to several μm.